1) Field of the Invention
This invention is an improvement on the inventor's prior work. Swain's U.S. Pat. No. 3,768,011 includes teaching of a clamp-on DC ammeter. Swain's application Ser. No. 08/579,395 includes teaching of a better clamp-on DC Ammeter. This MER2 invention teaches how to build still better sensors for clamp-on DC Ammeters for measuring continuous electrical current. MEC and MER are described in copending application Ser. No. 08/579,395.
2) Description of the Related Art
We build clamp-on DC Ammeters for measuring direct current as small as 5 milliamperes. Measurement accuracy can be damaged in many ways. One is zero offset error. This can be due to several things, one of which is the non-uniform magnetic field set up by magnetized material relatively close to the sensor. Copending application Ser. No. 08/579,395 reduced this error, but generally does not eliminate it. This invention teaches a counter intuitive way to still further reduce error due to nearby magnets so as to get even greater accuracy. A by-product is that the sensor's zero offset error due to the generally uniform magnetic field of the Earth is also reduced.